Imaging element and imaging device

ABSTRACT

An imaging element includes a first photoelectric conversion unit and a second photoelectric conversion unit that generates electric charges by photoelectric conversion, a first comparison unit that outputs a first signal based on a result of comparing a signal based on electric charges generated by the first photoelectric conversion unit and a reference signal, a first storage unit that stores a signal based on the first signal that is output by the first comparison unit, a second comparison unit that outputs a second signal based on a result of comparing a signal based on electric charges generated by the second photoelectric conversion unit and a reference signal, a second storage unit that stores a signal based on the second signal that is output from the second comparison unit, and a connection unit that connects or disconnect the first comparison unit and the second storage unit.

TECHNICAL FIELD

The present invention relates to an imaging element and an imagingdevice.

BACKGROUND ART

Conventionally, an imaging element having a storage unit that stores adigital value corresponding to the amount of light received by a pixeland a storage unit that temporarily stores a digital value for signalprocessing and horizontal transfer control is known (for example, referto Patent Literature 1).

CITATION LIST Patent Literature [Patent Literature 1]

PCT International Publication No. WO 2017/18215

SUMMARY OF INVENTION

According to a first aspect of the present invention, an imaging elementincludes a first photoelectric conversion unit and a secondphotoelectric conversion unit that generates electric charges byphotoelectric conversion, a first comparison unit that outputs a firstsignal based on a result of comparing a signal based on electric chargesgenerated by the first photoelectric conversion unit and a referencesignal, a first storage unit that stores a signal based on the firstsignal that is output by the first comparison unit, a second comparisonunit that outputs a second signal based on a result of comparing asignal based on electric charges generated by the second photoelectricconversion unit and a reference signal, a second storage unit thatstores a signal based on the second signal that is output from thesecond comparison unit, and a first connection unit that connects ordisconnect the first comparison unit and the second storage unit.

According to a second aspect of the present invention, an imaging deviceincludes the imaging element according to the first aspect, and ageneration unit that generates image data on the basis of a signaloutput from the imaging element.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram which shows a configuration example of an imagingdevice according to a first embodiment.

FIG. 2 is a block diagram which shows a configuration example of animaging element according to the first embodiment.

FIG. 3 is a circuit diagram which shows a configuration example of apart of the imaging element according to the first embodiment.

FIG. 4 is a diagram which describes reading processing of the imagingelement according to the first embodiment.

FIG. 5 is a diagram which describes an example of a method of addingpixel signals in the imaging element according to the first embodiment.

FIG. 6 is a diagram which describes another reading processing of theimaging element according to the first embodiment.

FIG. 7 is a diagram which describes another reading processing of theimaging element according to the first embodiment.

FIG. 8 is a diagram which describes another reading processing of theimaging element according to the first embodiment.

FIG. 9 is a diagram which describes another reading processing of theimaging element according to the first embodiment.

FIG. 10 is a diagram which performs a comparison in reading processingof the imaging element according to the first embodiment.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIG. 1 is a diagram which shows a configuration example of a camera 1that is an example of an imaging device according to a first embodiment.The camera 1 includes an image capturing optical system (an imageforming optical system) 2, an imaging element 3, a control unit 4, amemory 5, a display unit 6, and an operation unit 7. The image capturingoptical system 2 has a plurality of lenses including a focus adjustinglens (a focus lens) and an aperture diaphragm, and forms an image of asubject on the imaging element 3. The image capturing optical system 2may also be detached from the camera 1.

The imaging element 3 is an imaging element such as a CMOS image sensoror a CCD imaging sensor. The imaging element 3 receives a luminous fluxthat has passed through the image capturing optical system 2 andcaptures a subject image formed by the image capturing optical system 2.In the imaging element 3, a plurality of pixels having a photoelectricconversion unit are arranged in a two-dimensional shape (a row directionand a column direction). The photoelectric conversion element isconfigured by a photodiode (PD). The imaging element 3 generates asignal by performing photoelectric conversion on the received light, andoutputs the generated signal to the control unit 4.

The memory 5 is a recording medium such as a memory card. Image data, acontrol program, and the like are recorded in the memory 5. Writing datato the memory 5 and reading data from the memory 5 are controlled by thecontrol unit 4. The display unit 6 displays an image based on the imagedata, information regarding photographing such as a shutter speed and adiaphragm value, a menu screen, and the like. The operation unit 7includes various setting switches such as a release button, a powerswitch, and a switch for switching between various modes, and outputs asignal based on each operation to the control unit 4.

The control unit 4 is configured by a CPU, a processor such as an FPGAand an ASIC, and a memory such as a ROM or a RAM, and controls each partof the camera 1 based on the control program. The control unit 4supplies a signal that controls the imaging element 3 to the imagingelement 3 to control an operation of the imaging element 3. In addition,the control unit 4 performs various types of image processing on asignal output from the imaging element 3 to generate image data. Thecontrol unit 4 is also an image generation unit that generates imagedata, and generates still image data and moving image data on the basisof the signal output from the imaging element 3. The image processingincludes image processing such as gradation conversion processing andcolor interpolation processing.

The control unit 4 performs processing of individually reading signalsof all the pixels of the imaging element 3 and processing of mixing(adding) and reading signals of a plurality of pixels. The control unit4 controls the imaging element 3 to select (set) a method of reading thepixel signals. For example, the control unit 4 performs processing ofmixing and reading the signals of a plurality of pixels when a throughimage (a live-view image) of a subject is displayed on the display unit6 and moving image photography is performed. Moreover, the control unit4 performs processing of individually reading the signals of all thepixels when still image photography with high resolution is performed.

FIG. 2 is a block diagram which shows a configuration example of theimaging element according to the first embodiment. The imaging element 3is configured by laminating a first substrate 111 on which a pluralityof pixels 10 are formed and a second substrate 112 on which a pluralityof analog/digital conversion units (AD conversion units) 40 are formed.The first substrate 111 and the second substrate 112 are respectivelyconfigured by using a semiconductor substrate. Circuits provided on thefirst substrate 111 and circuits provided on the second substrate 112are electrically connected by bumps, electrodes, and the like.

The first substrate 111 has a plurality of pixels 10 arranged in atwo-dimensional manner. The pixel 10 outputs a photoelectric conversionsignal and a dark signal, which will be described below, to the secondsubstrate 112. In FIG. 2, 16 pixels 10 of 4 pixels in a row directionand 4 pixels in a column direction are shown with a pixel 10 at an upperleft corner set as a pixel 10(1,1) in a first row and a first column,and a pixel 10 at a lower right corner set as a pixel 10(4,4) in afourth row and a fourth column. The number and arrangement of pixelsarranged in the imaging element are not limited to those in the shownexample.

The second substrate 112 has a plurality of AD conversion units 40. Inthe present embodiment, the AD conversion unit 40 is provided for eachpixel 10. In FIG. 2, 16 AD conversion units 40 from an AD conversionunit 40(1,1) to an AD conversion unit 40(4,4) are shown. As will bedescribed below, the AD conversion unit 40 is configured to include acomparison unit and a storage unit, and converts an input photoelectricconversion signal and a dark signal into digital signals having thepredetermined number of bits, respectively.

FIG. 3 is a circuit diagram which shows a configuration example of apart of the imaging element according to the first embodiment. Theimaging element 3 includes a plurality of pixels 10, a plurality of ADconversion units 40, a reading control unit 60, a signal processing unit70, and an input/output unit 80.

A pixel 10 has a photoelectric conversion unit 11, a transfer unit 12, areset unit 13, a floating diffusion (FD) 14, an amplification unit 15,and a current source 16. The photoelectric conversion unit 11 is aphotodiode PD, which converts incident light into electric charges andaccumulates the photoelectrically converted electric charges. Thetransfer unit 12 is configured from a transistor M1 controlled by asignal TX, and transfers the electric charges photoelectricallyconverted by the photoelectric conversion unit 11 to the FD 14. Thetransistor M1 is a transfer transistor. The FD 14 accumulates (holds)the electric charges transferred to the FD 14. The current source 16generates a current for reading a signal from the pixel 10, and suppliesthe generated current to the signal line 18 and the amplification unit15.

The amplification unit 15 is configured from a transistor M3 whose gate(terminal) is connected to the FD 14, amplifies signals of electriccharges accumulated in the FD 14, and outputs the signals to the signalline 18. The transistor M3 is an amplification transistor. The resetunit 13 is configured from a transistor M2 controlled by a signal RST,discharges the electric charges accumulated in the FD 14, and resets avoltage of the FD 14. The transistor M2 is a reset transistor.

The pixel 10 sequentially outputs a signal (a dark signal) when thevoltage of the FD 14 is reset and a signal (a photoelectric conversionsignal) corresponding to an electric charge transferred from thephotoelectric conversion unit 11 to the FD 14 by the transfer unit 12 tothe signal line 18. The dark signal is an analog signal indicating areference level for the photoelectric conversion signal. In addition,the photoelectric conversion signal is an analog signal generated on thebasis of an electric charge photoelectrically converted by thephotoelectric conversion unit 11. The dark signal and the photoelectricconversion signal sequentially output from the pixel 10 are input to theAD conversion unit 40 via the signal line 18, a bump, and the like.

The AD conversion unit 40 has a comparison unit 20, a switch SW1, astorage unit 25, and a selection unit 30. The comparison unit 20 isconfigured to include a comparator circuit. A ramp signal ramp, which isa reference signal that changes with an elapse of time, is input to afirst terminal 21 of the comparison unit 20 from a signal generationcircuit (not shown). A signal (a photoelectric conversion signal or adark signal) output from the pixel 10 to the signal line 18 is amplifiedand input to a second terminal 22 of the comparison unit 20 directly orby an amplifier circuit (not shown). The comparison unit 20 compares asignal input from the pixel 10 with the reference signal, and outputs anoutput signal that is a result of the comparison from the outputterminal 23.

The comparison unit 20 is connected to the storage unit 25 via theswitch SW1. The switch SW1 is configured by a transistor, andelectrically connects or disconnects the comparison unit 20 and thestorage unit 25. When the switch SW1 is in an ON state, the switch SW1outputs an output signal of the comparison unit 20 to the storage unit25.

The storage unit 25 is configured by a plurality of latch circuitscorresponding to the number of bits of a digital signal to be stored.The output signal indicating the result of the comparison by thecomparison unit 20 is input to one input terminal (a G terminal) of eachlatch circuit via the switch SW1. A clock signal indicating a countvalue is input from a counter circuit (not shown) to the other inputterminal (a D terminal) of each latch circuit. In the example shown inFIG. 3, cnt<0> to cnt<n> indicating count values are input to the otherinput terminal (the D terminal) of each latch circuit, and the ADconversion unit 40 serves as an n-bit AD conversion circuit.

The storage unit 25 stores a count value according to an elapsed timefrom a start of comparison by the comparison unit 20 to an inversion ofa result of the comparison as a digital signal on the basis of an outputsignal of the comparison unit 20 and a clock signal from a countercircuit. In other words, the storage unit 25 stores a count valueaccording to a time until a magnitude relationship between a level of asignal output from the pixel 10 and a level of the reference signalchanges (inverts) as a digital signal on the basis of a signal outputfrom the comparison unit 20.

When a dark signal of a pixel 10 is input to the comparison unit 20, thecomparison unit 20 compares the dark signal with the reference signaland outputs a result of the comparison to the storage unit 25. On thebasis of the result of the comparison by the comparison unit 20 and aclock signal, the storage unit 25 stores the count value according tothe elapsed time from the start of the comparison by the comparison unit20 to the inversion of the result of the comparison as a digital signalbased on the dark signal. When a photoelectric conversion signal of thepixel 10 is input to the comparison unit 20, the comparison unit 20compares the photoelectric conversion signal with the reference signal,and outputs a result of the comparison to the storage unit 25. On thebasis of the result of the comparison by the comparison unit 20 and theclock signal, the storage unit 25 stores the count value according tothe elapsed time from the start of the comparison by the comparison unit20 to the inversion of the result of the comparison as the digitalsignal based on the photoelectric conversion signal. In this manner, theAD conversion unit 40 converts the photoelectric conversion signal,which is an analog signal, into a digital signal having thepredetermined number of bits, and converts the dark signal, which is ananalog signal, into a digital signal having the predetermined number ofbits.

The selection unit 30 is configured by a multiplexer controlled by asignal SEL, and a pixel signal (an n-bit digital signal in FIG. 3)converted into a digital signal is input from the storage unit 25. Theselection unit 30 outputs the pixel signal input from the storage unit25 to the signal line 50 (hereinafter, referred to as a data line). Thedata line 50 is configured by a plurality of signal lines correspondingto the number of bits of the digital signal output from the ADconversion unit 40. In the imaging element 3, data lines 50 (n signallines in FIG. 3) are provided for each column of the plurality of ADconversion units 40 arranged in a longitudinal direction, that is, in acolumn direction (a vertical direction).

The signal processing unit 70 is configured to include an amplifiercircuit, a decoder circuit, and the like. A pixel signal converted intoa digital signal (a digital signal based on a dark signal or a digitalsignal based on a photoelectric conversion signal) is input to thesignal processing unit 70 via the data line 50. The processing unit 70performs signal processing such as correlation double sampling and codeconversion processing on a signal input from the AD conversion unit 40via the data line 50, and outputs the signal to the input/output unit80. The input/output unit 80 has an input/output circuit correspondingto a high-speed interface such as those of SLVS and LVDS. Theinput/output unit 80 outputs (transmits) the signal input from thesignal processing unit 70 to the control unit 4 of the camera 1 at ahigh speed.

The reading control unit 60 is commonly provided in the plurality ofpixels 10 and the plurality of AD conversion units 40. The readingcontrol unit 60 is configured by a plurality of circuits including atiming generator, which are arranged dividedly on the first substrate111 and the second substrate 112. The reading control unit 60 may bearranged on either one of the first substrate 111 and the secondsubstrate 112, or may be arranged on a substrate different from thefirst substrate 112 and the second substrate 112.

The reading control unit 60 supplies signals such as the signal TX andthe signal RST that are controlled by the control unit 4 of the camera 1and described above to each pixel 10 to control the operation of eachpixel 10. The reading control unit 60 supplies a signal to a gate ofeach transistor of the pixel 10, and turns the transistor on (aconnected state, a conducting state, or a short-circuited state) orturns it off (a disconnected state, a non-conducting state, an openstate, or a cutoff state).

The reading control unit 60 supplies the signal SEL described above tothe selection unit 30 of each AD conversion unit 40 and controls theselection unit 30 of each AD conversion unit 40. When the selection unit30 is enabled (an on state) by the reading control unit 60, the pixelsignal converted into a digital signal, which is input from the storageunit 25, is output to the signal processing unit 70 via the data line50. The reading control unit 60 sequentially turns on the selection unit30 of each AD conversion unit 40, and outputs a pixel signal stored inthe storage unit 25 connected to the selection unit 30 that is turned onto the data line 50. It can be said that the reading control unit 60sequentially selects a plurality of AD conversion units 40 and reads apixel signal converted into a digital signal from the selected ADconversion unit 40. An n-bit pixel signal converted into a digitalsignal is input to the signal processing unit 70 for each data line 50.

FIG. 4 is a diagram which describes reading processing of the imagingelement according to the first embodiment. The imaging element 3 isprovided with a switch SW2 (a switch SW2 a to a switch SW2 h in FIG. 4)that connects or disconnects the comparison unit 20 of the AD conversionunit 40 and the storage unit 25 of an AD conversion unit 40 differentfrom the AD conversion unit 40. In the present embodiment, the switchSW2 connects an output terminal 23 of the comparison unit 20 of one ADconversion unit 40 and an input terminal (a G terminal) of the storageunit 25 of the other AD conversion unit 40 among two AD conversion units40 adjacent to each other in the row direction.

In the example shown in FIG. 4, the switch SW2 is provided between thecomparison unit 20 of each of AD conversion units 40 in an odd-numberedcolumn and the storage unit 25 of each of AD conversion units 40 in aneven-numbered column. The switch SW2 is configured by a transistor. Forexample, a switch SW2 a is a connection unit 2 a, and connects thecomparison unit 20 of an AD conversion unit 40(1,1) and the storage unit25 of an AD conversion unit 40(1,2) among AD conversion units 40 in afirst row. A switch SW2 e is a connection unit 2 e, and connects thecomparison unit 20 of an AD conversion unit 40(3,1) and the storage unit25 of an AD conversion unit 40(3,2) among AD conversion units 40 in athird row. The reading control unit 60 (refer to FIG. 3) suppliessignals to each of the switches SW2 a to SW2 h to control on and off ofeach switch.

The reading control unit 60 performs processing of individually readinga signal of each pixel of the imaging element 3 (individual readingprocessing) and processing of adding and reading signals of a pluralityof pixels (addition reading processing). In the individual readingprocessing, the reading control unit 60 sequentially selects an ADconversion unit 40 of the imaging element 3 from a first row to a fourthrow in units of rows, and reads a pixel signal from the selected ADconversion unit 40 in FIG. 4.

In the addition reading processing, the reading control unit 60 controlsa plurality of switches SW as shown in FIG. 5(a) and connects the FD 14of each of the plurality of pixels 10 to each other to add the signalsof the plurality of pixels. The reading control unit 60 may control aplurality of switch SWs as shown in FIG. 5(b), and connect theamplification unit 15 of a plurality of pixels 10 to the same signalline 18 to add the signals of the plurality of pixels. The readingcontrol unit 60 performs processing of selecting some AD conversionunits 40 to which a signal generated by adding the signals of aplurality of pixels is input (hereinafter, referred to as first ADconversion units) for each row or plural rows among the plurality of ADconversion units 40 of the imaging element 3 and reading the signals ofpixels.

In the present embodiment, the addition reading processing has a firstreading method, a second reading method, and a third reading method. Thefirst reading method is a method in which the first AD conversion unit40 is sequentially selected for each row, and a pixel signal convertedinto a digital signal is read. The first AD conversion unit 40 is an ADconversion unit 40 that is selected by thinning out AD conversion units40 of a specific row or column among all the AD conversion units 40. Inthe first AD conversion unit 40, an added pixel signal is input, and theadded pixel signal is converted into a digital signal.

The second reading method is a method in which the first AD conversionunit 40 is sequentially selected for each of a plurality of rows, and apixel signal that is converted into a digital signal is read.

The third reading method is a method in which AD conversion of a pixelsignal (for example, a photoelectric conversion signal) and reading of apixel signal converted to a digital signal (for example, a digitalsignal based on a dark signal) are performed at the same time (inparallel). The control unit 4 of the camera 1 controls the readingcontrol unit 60 to switch a reading method of a pixel signal.

(Individual Reading Processing)

In the individual reading processing, the reading control unit 60 turnson the switch SW1 of the plurality of AD conversion units 40 of theimaging element 3, and causes each AD conversion unit 40 to perform ADconversion. The reading control unit 60 sequentially selects theplurality of these AD conversion units 40 in units of rows, and causes apixel signal converted into a digital signal to be output from theselected AD conversion units 40 to the data line 50.

(First Reading Method of Addition Reading Processing)

In the first reading method, the reading control unit 60 turns on theswitches SW1 of the plurality of first AD conversion units 40, andcauses each of the plurality of first AD conversion units 40 to performAD conversion. The reading control unit 60 sequentially selects theplurality of these first AD conversion units 40 in units of rows, andcauses a pixel signal converted into a digital signal to be output fromthe selected first AD conversion units 40 to the data line 50. Asdescribed above, in the case of the first reading method, the readingcontrol unit 60 uses only the first AD conversion unit 40 among all theAD conversion units 40. Other AD conversion units 40 (hereinafter,referred to as second AD conversion units) different from the first ADconversion units 40 and the data line 50 to which these second ADconversion units 40 are connected are not used in the case of the firstreading method, and are brought into a pause state.

(Second Reading Method of Addition Reading Processing)

In the second reading method, the reading control unit 60 controls theswitch SW1 and the switch SW2 to use the storage unit 25 and theselection unit 30 of the second AD conversion unit 40, and the data line50 connected to the second AD conversion unit 40 in addition to thefirst AD conversion unit 40. In the second reading method, by using thedata lines 50 provided for different columns, it is possible tosimultaneously read a pixel signal converted into a digital signal fromthe AD conversion unit 40 of a plurality of rows. The imaging element 3can read a pixel signal in a shorter time than in a case where the firstAD conversion unit 40 is selected in units of rows and a pixel signal issequentially read by the data line 50.

(Third Reading Method of Addition Reading Processing)

Also in the case of the third reading method, the reading control unit60 uses the storage unit 25 and selection unit 30 of the second ADconversion unit 40 and the data line 50 connected to the second ADconversion unit 40 in addition to the first AD conversion unit 40. Thereading control unit 60 controls the switch SW1 and the switch SW2 andcontrol whether an output signal of the comparison unit 20 of the firstAD conversion unit 40 is output to the storage unit 25 of the first ADconversion unit 40 or the storage unit 25 of the second AD conversionunit 40. It can be said that the reading control unit 60 switches thestorage unit 25 which is an output destination of a result of thecomparison by the comparison unit 20 of the first AD conversion unit 40.

In the third reading method, the reading control unit 60 switches aconnection destination of the comparison unit 20 of the first ADconversion unit 40 to the storage unit 25 of the first AD conversionunit 40 or the storage unit 25 of the second AD conversion unit 40 whena dark signal is input to the comparison unit 20 of the first ADconversion unit 40 and when a photoelectric conversion signal is inputto the comparison unit 20 of the first AD conversion unit 40. Forexample, when a dark signal is input to the comparison unit 20 of thefirst AD conversion unit 40, the reading control unit 60 connects thecomparison unit 20 of the first AD conversion unit 40 and the storageunit 25 of the first AD conversion unit 40. The comparison unit 20 ofthe first AD conversion unit 40 outputs an output signal indicating aresult of comparing the dark signal and the reference signal to thestorage unit 25 of the first AD conversion unit 40 via the switch SW1.The storage unit 25 of the first AD conversion unit 40 stores a digitalsignal based on the dark signal on the basis of the output signal of thecomparison unit 20.

After the AD conversion of the dark signal is completed, the readingcontrol unit 60 starts reading the digital signal based on the darksignal from the storage unit 25 of the first AD conversion unit 40 tothe data line 50. Moreover, the reading control unit 60 connects thecomparison unit 20 of the first AD conversion unit 40 and the storageunit 25 of the second AD conversion unit 40. At this time, when aphotoelectric conversion signal is input to the comparison unit 20 ofthe first AD conversion unit 40, the comparison unit 20 of the first ADconversion unit 40 outputs an output signal indicating a result ofcomparing the photoelectric conversion signal and the reference signalto the storage unit 25 of the second AD conversion unit 40 via theswitch SW2. The storage unit 25 of the second AD conversion unit 40stores a digital signal based on the photoelectric conversion signal onthe basis of the output signal of the comparison unit 20 of the first ADconversion unit 40.

In this manner, in the third reading method, AD conversion is performedusing different storage units 25 depending on whether AD conversion of adark signal is performed or AD conversion of a photoelectric conversionsignal is performed. As a result, reading of a digital signal based on adark signal and AD conversion of a photoelectric conversion signal canbe performed in parallel. Similarly, reading of a digital signal basedon a photoelectric conversion signal and AD conversion of a dark signalcan be performed in parallel. For this reason, the imaging element 3does not need to wait for a completion of the processing of reading apixel signal to the data line 50 to start next AD conversion processing,and can read a pixel signal in a short time. In the followingdescription, the individual reading processing and the first to thirdreading methods of the addition reading processing will be furtherdescribed with reference to FIGS. 4 to 10.

(Individual Reading Processing)

When the individual reading processing is instructed by the control unit4, the reading control unit 60 turns on each switch SW1 of the ADconversion unit 40(1,1) to the AD conversion unit 40(4,4) as shown inFIG. 4, and turns off the switches SW2 a to SW2 h.

The reading control unit 60 turns on each of the reset units 13 of thepixel 10(1,1) to the pixel 10(4,4). As a result, a voltage of each FD 14is reset at each pixel 10. Each dark signal of the pixel 10(1,1) to thepixel 10(4,4) is output to each of the AD conversion unit 40(1,1) to theAD conversion unit 40(4,4) via a signal line 18 connected to each pixel10. The AD conversion unit 40(1,1) to the AD conversion unit 40(4,4)convert the input dark signal into a digital signal. The storage units25 of each of the AD conversion unit 40(1,1) to the AD conversion unit40(4,4) store a digital signal based on a dark signal of the pixel10(1,1) to pixel 10(4,4), respectively.

The reading control unit 60 turns on each of the selection units 30 ofthe AD conversion unit 40(1,1) to an AD conversion unit 40(1,4), whichare AD conversion units 40 in a first row, and turns off each ofselection units 30 of AD conversion units 40 in the rows other than thefirst row. As a result, digital signals based on dark signals of the ADconversion unit 40(1,1) to the AD conversion unit 40(1,4) are output toeach of the data lines 50 a to 50 d via each of the selection unit 30 ofthe AD conversion units 40.

After reading the digital signal based on a dark signal from each of theAD conversion units 40 in the first row, the reading control unit 60turns on each of the selection units 30 of an AD conversion unit 40(2,1)to an AD conversion unit 40(2,4), which are AD conversion units 40 in asecond row, and turns off each of the selection units 30 of ADconversion units 40 in the rows other than the second row. As a result,digital signals based on dark signals of the AD conversion unit 40(2,1)to the AD conversion unit 40(2,4) are output to each of the data lines50 a to 50 d via each of the selection units 30 of the AD conversionunits 40. In addition, similarly, the reading control unit 60sequentially selects AD conversion units 40 of a third row andsubsequent rows for each row in an order of the third row, a fourth row,and a fifth row, and reads a digital signal based on a dark signal fromeach of the selected AD conversion units 40.

The reading control unit 60 turns on each of the transfer units 12 ofthe pixel 10(1,1) to the pixel 10(4,4). As a result, at each pixel 10,electric charges photoelectrically converted by each PD 11 aretransferred to the FD 14. Photoelectric conversion signals of each ofthe pixel 10(1,1) to the pixel 10(4,4) are output to the AD conversionunit 40(1,1) to the AD conversion unit 40(4,4) via the signal line 18connected to each pixel 10, respectively. The AD conversion unit 40(1,1)to the AD conversion unit 40(4,4) convert the input photoelectricconversion signals into digital signals. The storage units 25 of each ofthe AD conversion unit 40(1,1) to the AD conversion unit 40(4,4) storedigital signals based on photoelectric conversion signals of the pixel10(1,1) to the pixel 10(4,4), respectively.

The reading control unit 60 selects AD conversion units for each row inthe order of the first row, the second row, the third row, the fourthrow, and the fifth row, and read a digital signal based on aphotoelectric conversion signal from each selected AD conversion unit 40in the same manner as when it reads a digital signal based on a darksignal from each AD conversion unit 40.

In this manner, in the individual reading processing, the readingcontrol unit 60 individually reads the signals of pixels of the imagingelement 3. The digital signal based on a dark signal and the digitalsignal based on a photoelectric conversion signal that are sequentiallyoutput to the data lines 50 a to 50 d are subjected to signal processingsuch as correlation double sampling performed by the signal processingunit 70 (refer to FIG. 3), and then are output to the control unit 4 viathe input/output unit 80.

(First to Third Reading Methods of Addition Reading Processing)

In the first to third reading methods of the addition readingprocessing, the reading control unit 60 adds the signals of a pluralityof pixels for each of the plurality of pixels. In the followingdescription, an example will be described in which, for every fourpixels of 2 pixels×2 pixels, the signals of these four pixels are added.A signal obtained by adding a signal of the pixel 10(1,1), a signal ofthe pixel 10(1,2), a signal of the pixel 10(2,1), a signal of the pixel10(2,2) is input to the AD conversion unit 40(1,1). A signal obtained byadding signals of each of a pixel 10(1,3), a pixel 10(1,4), a pixel10(2,3), and a pixel 10(2,4) is input to the AD conversion unit 40(1,3).In addition, a signal obtained by adding signals of each of a pixel10(3,1), a pixel 10(3,2), a pixel 10(4,1), and a pixel 10(4,2) is inputto the AD conversion unit 40(3,1), and a signal obtained by addingsignals of each of a pixel 10(3,3), a pixel 10(3,4), a pixel 10(4,3),and a pixel 10(4,4) is input to the AD conversion unit 40(3,3).

The AD conversion unit 40(1,1), the AD conversion unit 40(1,3), the ADconversion unit 40(3,1), and the AD conversion unit 40(3,3) function asthe first AD conversion unit described above. In FIG. 6, these ADconversion units 40 surrounded by thick lines are examples of ADconversion units used in the case of the first reading method. The ADconversion units 40 surrounded by thick lines in FIG. 7 are examples ofAD conversion units used in the case of the second reading method, andthe AD conversion units 40 surrounded by thick lines in FIGS. 8 and 9are examples of AD conversion units used in the case of the thirdreading method.

(First Reading Method of Addition Reading Processing)

When the first reading method is instructed by the control unit 4, thereading control unit 60 turns on the switch SW1 of each of the ADconversion unit 40(1,1), the AD conversion unit 40(1,3), the ADconversion unit 40(3,1), and the AD conversion unit 40(3,3), as shown inFIG. 6, and turns off the switches SW2 a to SW2 h. When an added darksignal is input, the AD conversion unit 40(1,1), the AD conversion unit40(1,3), the AD conversion unit 40(3,1), and the AD conversion unit40(3,3) convert the dark signal into a digital signal. The storage units25 of each of the AD conversion unit 40(1,1), the AD conversion unit40(1,3), the AD conversion unit 40(3,1), and the AD conversion unit40(3,3) store a digital signal based on the added dark signal,respectively.

The reading control unit 60 turns on the selection units 30 of the ADconversion unit 40(1,1) and the AD conversion unit 40(1,3) in the firstrow, respectively, and turns off the selection units 30 of other ADconversion units 40 different from the AD conversion unit 40(1,1) andthe AD conversion unit 40(1,3). As a result, a digital signal based onan added dark signal of the AD conversion unit 40(1,1) is output to thedata line 50 a via the selection unit 30 of the AD conversion unit40(1,1). Moreover, a digital signal based on an added dark signal of theAD conversion unit 40(1,3) is output to the data line 50 c via theselection unit 30 of the AD conversion unit 40(1,3).

After the digital signals based on the dark signals from the ADconversion unit 40(1,1) and the AD conversion unit 40(1,3) in the firstrow are read, the reading control unit 60 turns on the selection units30 of the AD conversion unit 40(3,1) and the AD conversion unit 40(3,3)in the third row, respectively. Moreover, the reading control unit 60turns off the selection units 30 of other AD conversion units 40different from the AD conversion unit 40(3,1) and the AD conversion unit40(3,3), respectively. As a result, a digital signal based on an addeddark signal of the AD conversion unit 40(3,1) is output to the data line50 a via the selection unit 30 of the AD conversion unit 40(3,1).Furthermore, a digital signal based on an added dark signal of the ADconversion unit 40(3,3) is output to the data line 50 c via theselection unit 30 of the AD conversion unit 40(3,3). After that, in thesame manner, the reading control unit 60 sequentially selects ADconversion units 40 for each row, and reads a digital signal based on adark signal from each of the selected AD conversion units 40.

When an added photoelectric conversion signal is input, the ADconversion unit 40(1,1), the AD conversion unit 40(1,3), the ADconversion unit 40(3,1), and the AD conversion unit 40(3,3) convert thephotoelectric conversion signal to a digital signal. The storage units25 of each of the AD conversion unit 40(1,1), the AD conversion unit40(1,3), the AD conversion unit 40(3,1), and the AD conversion unit40(3,3) store a digital signal based on an added photoelectricconversion signal, respectively. The reading control unit 60sequentially selects AD conversion units 40 for each row and reads adigital signal based on a photoelectric conversion signal from each ofthe selected AD conversion units 40 in the same manner as when a digitalsignal based on a dark signal is read from each AD conversion unit 40.

In this manner, in the first reading method, the reading control unit 60sequentially selects some AD conversion units 40 among all the ADconversion units 40 of the imaging element 3 for each row, and reads apixel signal converted into a digital signal. The digital signal basedon a dark signal and the digital signal based on a photoelectricconversion signal sequentially output to the data lines 50 a and 50 care output to the control unit 4 by the input/output unit 80 after beingsubjected to signal processing by the signal processing unit 70.

(Second Reading Method of Addition Reading Processing)

When the second reading method is instructed by the control unit 4, thereading control unit 60 turns on each switch SW1 of the AD conversionunit 40(1,1) and the AD conversion unit 40(1,3) as shown in FIG. 7. Inaddition, the reading control unit 60 turns on the switch SW2 e and theswitch SW2 f. When the switch SW2 e is turned on, the comparison unit 20of the AD conversion unit 40(3,1) and the storage unit 25 of the ADconversion unit 40(3,2) are electrically connected. Furthermore, whenthe switch SW2 f is turned on, the comparison unit 20 of the ADconversion unit 40(3,3) and the storage unit 25 of the AD conversionunit 40(3,4) are electrically connected. The AD conversion unit 40(3,2)and the AD conversion unit 40(3,4) function as the second AD conversionunit described above.

When an added dark signal is input, the AD conversion unit 40(1,1) andthe AD conversion unit 40(1,3) convert the dark signal into a digitalsignal. The storage units 25 of each of the AD conversion unit 40(1,1)and the AD conversion unit 40(1,3) store a digital signal based on anadded dark signal, respectively.

When an added dark signal is input, the comparison unit 20 of the ADconversion unit 40(3,1) outputs an output signal indicating a result ofcomparing the added dark signal and the reference signal to the storageunit 25 of the AD conversion unit 40(3,2) via the switch SW2 e. Thestorage unit 25 of the AD conversion unit 40(3,2) stores a digitalsignal based on the added dark signal on the basis of the output signalof the comparison unit 20 of the AD conversion unit 40(3,1). In thismanner, the added dark signal input to the comparison unit 20 of the ADconversion unit 40(3,1) is converted into a digital signal by thecomparison unit 20 of the AD conversion unit 40(3,1) and the storageunit 25 of the AD conversion unit 40(3,2).

When an added dark signal is input, the comparison unit 20 of the ADconversion unit 40(3,3) outputs an output signal indicating a result ofcomparing the dark signal and the reference signal to the storage unit25 of the AD conversion unit 40(3,4) via the switch SW2 f. The storageunit 25 of the AD conversion unit 40(3,4) stores a digital signal basedon the added dark signal on the basis of the output signal of thecomparison unit 20 of the AD conversion unit 40(3,3). In this manner,the added dark signal input to the comparison unit 20 of the ADconversion unit 40(3,3) is converted into a digital signal by thecomparison unit 20 of the AD conversion unit 40(3,3) and the storageunit 25 of the AD conversion unit 40(3,4).

The reading control unit 60 turns on the selection units 30 of each ofthe AD conversion unit 40(1,1) and the AD conversion unit 40(1,3) in thefirst row, and the selection units 30 of each of the AD conversion unit40(3,2) and the AD conversion unit 40(3,4) in the third row,respectively. Moreover, the reading control unit 60 turns off theselection units 30 of other AD conversion units 40 different from the ADconversion unit 40(1,1), the AD conversion unit 40(1,3), the ADconversion unit 40(3,2), and the AD conversion unit 40(3,4).

The added dark signal input to the comparison unit 20 of the ADconversion unit 40(1,1) is converted into a digital signal by the ADconversion unit 40(1,1) as schematically shown by an arrow 90 a, andthen is output to the data line 50 a via the selection unit 30 of the ADconversion unit 40(1,1). Moreover, the added dark signal input to thecomparison unit 20 of the AD conversion unit 40(3,1) is, asschematically shown by an arrow 90 b, converted into a digital signal bythe comparison unit 20 of the AD conversion unit 40(3,1) and the storageunit 25 of the AD conversion unit 40(3,2), and then is output to thedata line 50 b via the selection unit 30 of the AD conversion unit40(3,2).

The added dark signal input to the comparison unit 20 of the ADconversion unit 40(1,3) is converted into a digital signal by the ADconversion unit 40(1,3) as schematically shown by an arrow 90 c, andthen is output to the data line 50 c via the selection unit 30 of the ADconversion unit 40(1,3). Moreover, the added dark signal input to thecomparison unit 20 of the AD conversion unit 40(3,3) is converted into adigital signal by the comparison unit 20 of the AD conversion unit40(3,3) and the storage unit 25 of the AD conversion unit 40(3,4) asschematically shown by an arrow 90 d, and then is output to the dataline 50 d via the selection unit 30 of the AD conversion unit 40(3,4).After that, in the same manner, the reading control unit 60 sequentiallyselects AD conversion units 40 for each two rows, and reads a digitalsignal based on a dark signal from each of the selected AD conversionunits 40.

When an added photoelectric conversion signal is input, the ADconversion unit 40(1,1) and the AD conversion unit 40(1,3) convert thephotoelectric conversion signal into a digital signal. The storage units25 of each of the AD conversion unit 40(1,1) and the AD conversion unit40(1,3) store a digital signal based on an added photoelectricconversion signal, respectively. The added photoelectric conversionsignal input to the comparison unit 20 of the AD conversion unit 40(3,1)is converted into a digital signal by the comparison unit 20 of the ADconversion unit 40(3,1) and the storage unit 25 of the AD conversionunit 40(3,2), and stored in the storage unit 25 of the AD conversionunit 40(3,2). In addition, the added photoelectric conversion signalinput to the comparison unit 20 of the AD conversion unit 40(3,3) isconverted into a digital signal by the comparison unit 20 of the ADconversion unit 40(3,3) and the storage unit 25 of the AD conversionunit 40(3,4), and stored in the storage unit 25 of the AD conversionunit 40(3,4).

The reading control unit 60 sequentially selects AD conversion units 40for each two rows, and reads a digital signal based on a photoelectricconversion signal from each of the selected AD conversion units 40 inthe same manner as when the digital signal based on a dark signal fromeach AD conversion unit 40 is read.

In this manner, in the second reading method, the reading control unit60 controls the switch SW1 and the switch SW2 such that an AD conversionunit 40 that is in the pause state in the case of the first readingmethod and the data lines 50 b and 50 d connected to the AD conversionunit 40 are also used. For this reason, the reading control unit 60 cansequentially select AD conversion units 40 for each two rows and read apixel signal converted into a digital signal. As a result, a pixelsignal can be read in a shorter time than when AD conversion units 40are sequentially selected for each row to read a pixel signal. Thedigital signal based on a dark signal and the digital signal based on aphotoelectric conversion signal sequentially output to the data lines 50a to 50 d are output to the control unit 4 by the input/output unit 80after being subjected to signal processing by the signal processing unit70.

(Third Reading Method of Addition Reading Processing)

FIGS. 8 and 9 are diagrams which describe the reading processing of animaging element when the third reading method is instructed by thecontrol unit 4. FIG. 8 shows a connection state of the switch SW1 andthe switch SW2 when an added dark signal is input to the comparison unit20 of the AD conversion unit 40. FIG. 9 shows the connection state ofthe switch SW1 and the switch SW2 when an added photoelectric conversionsignal is input to the comparison unit 20 of the AD conversion unit 40.In the examples shown in FIGS. 8 and 9, the AD conversion unit 40(1,2),the AD conversion unit 40(1,4), the AD conversion unit 40(3,2), and theAD conversion unit 40(3,4) function as the second AD conversion unitdescribed above.

When an added dark signal is input to the comparison unit 20 of the ADconversion unit 40, the reading control unit 60 turns on each switch SW1of the AD conversion unit 40(1,1), the AD conversion unit 40(1,3), theAD conversion unit 40(3,1), and the AD conversion unit 40(3,3) as shownin FIG. 8. Moreover, the reading control unit 60 turns off the switchesSW2 a to SW2 h.

The reading control unit 60 causes each of the AD conversion unit40(1,1), the AD conversion unit 40(1,3), the AD conversion unit 40(3,1),and the AD conversion unit 40(3,3) to perform AD conversion on an addeddark signal. For example, an added dark signal input to the comparisonunit 20 of the AD conversion unit 40(1,1) is converted into a digitalsignal by the AD conversion unit 40(1,1) as schematically shown by anarrow 91 a, and stored in the storage unit 25 of the AD conversion unit40(1,1). Moreover, an added dark signal input to the comparison unit 20of the AD conversion unit 40(1,3) is converted into a digital signal bythe AD conversion unit 40(1,3) as schematically shown by an arrow 91 c,and stored in the storage unit 25 of the AD conversion unit 40(1,3).

At the same time as the AD conversion of a dark signal, the readingcontrol unit 60 reads a digital signal based on a photoelectricconversion signal stored at the time of AD conversion of a previousphotoelectric conversion signal from the storage units 25 of each of theAD conversion unit 40(1,2), the AD conversion unit 40(1,4), the ADconversion unit 40(3,2), and the AD conversion unit 40(3,4). Forexample, as schematically shown by an arrow 92 b, a digital signal basedon an added photoelectric conversion signal is output to the data line50 b from the storage unit 25 of the AD conversion unit 40(1,2).Furthermore, as schematically shown by an arrow 92 d, a digital signalbased on an added photoelectric conversion signal is output to the dataline 50 d from the storage unit 25 of the AD conversion unit 40(1,4).After that, in the same manner, the reading control unit 60 sequentiallyselects AD conversion units 40 for each row, and reads a digital signalbased on a photoelectric conversion signal from each of the selected ADconversion units 40.

When an added photoelectric conversion signal is input to the comparisonunit 20 of the AD conversion unit 40, the reading control unit 60 turnsoff each switch SW1 of the AD conversion unit 40(1,1), the AD conversionunit 40(1,3), the AD conversion unit 40(3,1), and the AD conversion unit40(3,3) as shown in FIG. 9. Furthermore, the reading control unit 60turns on the switch SW2 a, the switch SW2 b, the switch SW2 e, and theswitch SW2 f.

The reading control unit 60 causes each of the comparison unit 20 of theAD conversion unit 40(1,1) and the storage unit 25 of the AD conversionunit 40(1,2), the comparison unit 20 of the AD conversion unit 40(1,3)and the storage unit 25 of the AD conversion unit 40(1,4), thecomparison unit 20 of the AD conversion unit 40(3,1) and the storageunit 25 of the AD conversion unit 40(3,2), and the comparison unit 20 ofthe AD conversion unit 40(3,3) and the storage unit 25 of the ADconversion unit 40(3,4) to perform AD conversion on an addedphotoelectric conversion signal. For example, an added photoelectricconversion signal input to the comparison unit 20 of the AD conversionunit 40(1,1) is converted into a digital signal by the comparison unit20 of the AD conversion unit 40(1,1) and the storage unit 25 of the ADconversion unit 40(1,2) as schematically shown by an arrow 91 b, andstored in the storage unit 25 of the AD conversion unit 40(1,2).Moreover, an added photoelectric conversion signal input to thecomparison unit 20 of the AD conversion unit 40(1,3) is converted into adigital signal by the comparison unit 20 and the AD conversion unit40(1,3) and the storage unit 25 of the AD conversion unit 40(1,4) asschematically shown by an arrow 91 d, and stored in the storage unit 25of the AD conversion unit 40(1,4).

At the same time as AD conversion of a photoelectric conversion signal,the reading control unit 60 reads a digital signal based on a darksignal stored at the time of the AD conversion of a previous dark signalfrom the storage units 25 of each of the AD conversion unit 40(1,1), theAD conversion unit 40(1,3), the AD conversion unit 40(3,1), and the ADconversion unit 40(3,3). For example, as schematically shown by an arrow92 a, a digital signal based on an added dark signal is output to thedata line 50 a from the storage unit 25 of the AD conversion unit40(1,1). Furthermore, as schematically shown by an arrow 92 c, a digitalsignal based on an added dark signal is output to the data line 50 cfrom the storage unit 25 of the AD conversion unit 40(1,3). After that,in the same manner, the reading control unit 60 sequentially selects ADconversion units 40 for each row, and reads a digital signal based on aphotoelectric conversion signal from each of the selected AD conversionunits 40.

In this manner, in the third reading method, the reading control unit 60controls the switch SW1 and the switch SW2 to perform AD conversionusing different storage units 25 depending on whether AD conversion of adark signal is performed or AD conversion of a photoelectric conversionsignal is performed. As a result, the imaging element 3 can perform ADconversion of a pixel signal and reading of a pixel signal convertedinto a digital signal to the data line 50 in parallel. For this reason,a pixel signal can be read in a short time.

(Comparison in First to Third Reading Methods of Addition ReadingProcessing)

FIG. 10 is a diagram which compares the first to third reading methodsof the addition reading processing of the imaging element according tothe first embodiment. FIG. 10(a) shows the processing in the case of thefirst reading method, FIG. 10(b) shows the processing in the case of thesecond reading method, and FIG. 10(c) shows the processing in the caseof the third reading method. Moreover, in FIGS. 10(a) to 10(c), readingprocessing of a dark signal from the pixel 10, AD conversion processingof a dark signal, reading processing of a digital signal based on a darksignal, reading processing of a photoelectric conversion signal from thepixel 10, AD conversion processing of a photoelectric conversion signal,and reading processing of a digital signal based on a photoelectricconversion signal are shown side by side on the same time axis.

In the case of the second reading method of FIG. 10 (b), as describedabove, the reading control unit 60 sequentially selects AD conversionunits 40 for each two rows and reads a digital signal based on a darksignal and a digital signal based on a photoelectric conversion signal.For this reason, the reading control unit 60 can read the digital signalbased on a dark signal from each AD conversion unit 40 in about ½ timeand can also read the digital signal based on a photoelectric conversionsignal from each AD conversion unit 40 in about ½ time as compared withthe case of the first reading method of FIG. 10(a). As a result, theimaging element 3 can improve a frame rate at the time of photography.

In the case of the third reading method of FIG. 10 (c), as describedabove, the reading control unit 60 performs the AD conversion of a darksignal (or a photoelectric conversion signal) read from a pixel andreading of a photoelectric conversion signal converted into a digitalsignal (or a dark signal) in parallel. Therefore, the imaging element 3can further improve the frame rate at the time of photography ascompared with the case of the second reading method of FIG. 10(b).

It is considered to provide a storage unit for AD conversion and astorage unit for reading a signal to the data line 50 separately foreach pixel 10, but, in this case, an area of the imaging element willincrease. In the present embodiment, it is not necessary to separatelyprovide the storage unit for AD conversion and the storage unit forreading a signal to the data line 50, and thus it is possible to preventthe area of the imaging element from increasing.

According to the embodiment described above, the following effects canbe obtained.

(1) The imaging element 3 includes a first photoelectric conversion unit11 and a second photoelectric conversion unit 11 that generate electriccharges by photoelectric conversion, a first comparison unit 20 thatoutputs a first signal based on a result of comparing a signal based onthe electric charges generated by the first photoelectric conversionunit 11 with a reference signal, a first storage unit 25 that stores asignal based on the first signal that is output from the firstcomparison unit 20, a second comparison unit 20 that outputs a secondsignal based on a result of comparing a signal based on the electriccharges generated by the second photoelectric conversion unit 11 withthe reference signal, a second storage unit 25 that stores a signalbased on the second signal that is output from the second comparisonunit 20, a first connection unit (the switch SW2) capable of connectingor disconnecting the first comparison unit 20 and the second storageunit 25, and a control unit (a reading control unit) that controls thefirst connection unit and controls whether the first signal is output tothe first storage unit or the second storage unit. Therefore, thereading control unit 60 according to the present embodiment can shortenreading time of a pixel signal by controlling the switch SW2 andperforming reading processing of the pixel signal.

(2) In the present embodiment, the imaging element 3 performs the secondreading method and the third reading method by controlling the switchSW1 and the switch SW2. As a result, the reading processing of a pixelsignal can be performed at a high speed. In addition, a frame rate atthe time of capturing an image can be improved.

The following modifications are also within the scope of the presentinvention, and one or more of modified examples can be combined with theembodiment described above.

Modified Example 1

In the embodiment described above, an example in which the readingcontrol unit 60 performs addition reading processing by adding signalsof a plurality of pixels has been described. The reading control unit 60may perform processing of thinning out pixels of a specific row orcolumn among all the pixels to read a signal (thinning-out readingprocessing). In the case of thinning-out reading processing, the readingcontrol unit 60 may perform the same reading method as the first tothird reading methods described above.

Modified Example 2

In the embodiment described above, an example in which the imagingelement 3 is configured by laminating the first substrate 111 and thesecond substrate 112 has been described. However, the first substrate111 and the second substrate 112 may not be laminated.

Modified Example 3

In the embodiment described above, an example in which the data line 50is configured by a plurality of signal lines corresponding to the numberof bits of a digital signal output from the AD conversion unit 40 hasbeen described. The data line 50 may be one signal line or an arbitrarynumber of signal lines.

Modified Example 4

In the embodiment and modified examples described above, an example inwhich a photodiode is used as a photoelectric conversion unit has beendescribed. However, a photoelectric conversion film (an organicphotoelectric film) may be used as the photoelectric conversion unit.

Modified Example 5

The imaging element and the imaging device described in the embodimentsand modified examples described above may be applied for cameras,smartphones, tablets, cameras embedded in PCs, in-vehicle cameras,cameras mounted on unmanned aerial vehicles (drones, radio-controlledvehicles, and the like), and the like.

Although various embodiments and modified examples have been describedabove, the present invention is not limited to these contents. Otheraspects considered within the scope of the technical idea of the presentinvention are also included within the scope of the present invention.

The disclosure content of the next priority basic application isincorporated herein as a quotation.

Japanese Patent Application No. 2019-69145 (filed on Mar. 29, 2019)

REFERENCE SIGNS LIST

-   -   1 Imaging device    -   3 Imaging element    -   4 Control unit    -   10 Pixel    -   11 Photoelectric conversion unit    -   20 Comparison unit    -   25 Storage unit    -   40 AD conversion unit    -   60 Reading control unit

1. An imaging element comprising: a first photoelectric conversion unitand a second photoelectric conversion unit that generates electriccharges by photoelectric conversion; a first comparison unit thatoutputs a first signal based on a result of comparing a signal based onelectric charges generated by the first photoelectric conversion unitand a reference signal; a first storage unit that stores a signal basedon the first signal that is output by the first comparison unit; asecond comparison unit that outputs a second signal based on a result ofcomparing a signal based on electric charges generated by the secondphotoelectric conversion unit and the reference signal; a second storageunit that stores a signal based on the second signal that is output fromthe second comparison unit; and a first connection unit that connects ordisconnect the first comparison unit and the second storage unit.
 2. Theimaging element according to claim 1, wherein the second storage unitstores a signal based on the first signal when the second storage unitis connected to the first comparison unit by the first connection unit.3. The imaging element according to claim 1, further comprising: acontrol unit that controls the first connection unit and control whetherthe first signal is output to the first storage unit or the secondstorage unit.
 4. The imaging element according to claim 3, wherein thecontrol unit causes the first connection unit to connect the firstcomparison unit and the second storage unit and causes the first signalto be output to the second storage unit.
 5. The imaging elementaccording to claim 3, further comprising: a second connection unit thatconnects or disconnect the first comparison unit and the first storageunit; and a third connection unit that connects or disconnect the secondcomparison unit and the second storage unit, wherein the control unitcontrols the second connection unit and the third connection unit. 6.The imaging element according to claim 5, wherein the control unitcauses the second connection unit to disconnect the first comparisonunit and the first storage unit and causes the third connection unit todisconnect the second comparison unit and the second storage unit whilethe first connection unit connects the first comparison unit and thesecond storage unit.
 7. The imaging element according to claim 5,wherein the control unit causes the second connection unit to connectthe first comparison unit and the first storage unit and causes thethird connection unit to connect the second comparison unit and thesecond storage unit while the first connection unit disconnects thefirst comparison unit and the second storage unit.
 8. The imagingelement according to claim 3, further comprising: a first signal linefrom which a signal stored in the first storage unit is output; and asecond signal line from which a signal stored in the second storage unitis output, wherein a signal based on the first signal stored in thesecond storage unit is output to the second signal line when the firstconnection unit connects the first comparison unit and the secondstorage unit.
 9. The imaging element according to claim 8, wherein thecontrol unit causes the first connection unit to connect the firstcomparison unit and the second storage unit when a signal based on thefirst signal is output using the second signal line.
 10. The imagingelement according to claim 8, wherein a signal based on the first signalstored in the first storage unit is output to the first signal line anda signal based on the second signal stored in the second storage unit isoutput to the second signal line when the first connection unitdisconnects the first comparison unit and the second storage unit. 11.The imaging element according to claim 8, wherein the control unitcauses the first connection unit to disconnect the first comparison unitand the second storage unit when a signal based on the first signal isoutput using the first signal line and a signal based on the secondsignal is output using the second signal line.
 12. The imaging elementaccording to claim 8, further comprising: a third photoelectricconversion unit that generates electric charges by photoelectricconversion; a third comparison unit that outputs a third signal based ona result of comparing a signal based on electric charges generated bythe third photoelectric conversion unit and a reference signal; and athird storage unit that stores a signal based on the third signal thatis output by the third comparison unit, wherein the control unit causesthe first connection unit to connect the first comparison unit and thesecond storage unit and outputs a signal based on the first signal usingthe second signal line when a signal based on the third signal is outputusing the first signal line.
 13. The imaging element according to claim12, wherein the control unit causes the first connection unit to connectthe first comparison unit and the second storage unit and outputs asignal based on the first signal stored in the second storage unit tothe second signal line when a signal based on the third signal stored inthe third storage unit is output to the first signal line.
 14. Theimaging element according to claim 3, further comprising: anaccumulation unit that accumulates electric charges generated by thefirst photoelectric conversion unit; and a reset unit that resetselectric charges accumulated in the accumulation unit, wherein the firstcomparison unit outputs a fourth signal based on a result of comparing asignal after electric charges accumulated in the accumulation unit arereset and the reference signal, and the control unit controls the firstconnection unit and controls whether to output the fourth signal to thefirst storage unit or the second storage unit.
 15. The imaging elementaccording to claim 14, wherein the control unit causes the firstconnection unit to connect the first comparison unit and the secondstorage unit and outputs the fourth signal to the second storage unitwhen the first signal is output to the first storage unit.
 16. Theimaging element according to claim 15, wherein the second storage unitstores a signal based on the fourth signal when the fourth signal isoutput.
 17. The imaging element according to claim 14, wherein thecontrol unit causes the first connection unit to connect the firstcomparison unit and the second storage unit and outputs the first signalto the second storage unit when the fourth signal is output to the firststorage unit.
 18. The imaging element according to claim 17, wherein thefirst storage unit stores a signal based on the fourth signal when thefourth signal is output.
 19. The imaging element according to claim 1,further comprising: a first substrate that is provided with the firstphotoelectric conversion unit and the second photoelectric conversionunit; and a second substrate that is laminated on the first substrateand is provided with the first storage unit and the second storage unit.20. An imaging device comprising: the imaging element according to claim1; and a generation unit that generates image data on the basis of asignal output from the imaging element.